Measurement of steroid hormone receptors in breast cancer patients on tamoxifen

Summary Estrogen (ER) and progesterone receptor (PgR) positive breast tumors often respond to tamoxifen, but ultimately progress as they become tamoxifen resistant. An accurate assessment of receptor status in specimens from tamoxifen-resistant patients could help to understand potential mechanisms of resistance and to predict response to second line hormonal therapies. However, since tamoxifen itself can affect ER and PgR determinations, assay results can be misleading. We measured ER and PgR by both ligand binding (LBA) and immunohistochemical (IHC) assays in 34 tumors from patients on tamoxifen, 30 of whom were displaying resistance to the drug. These tumors were classified into several receptor phenotypes. Eleven patients, 8 of whom were clearly progressing, expressed both receptors while on tamoxifen. ER was significantly less often negative when measured by IHC, suggesting that ER status by LBA was falsely negative in this group due to receptor occupancy by tamoxifen. Six patients had no detectable ER by LBA or IHC but still expressed PgR. The presence of PgR suggests that ER could still be functional, though undetectable, in these tumors, or that PgR is constitutively expressed by them. Finally, 12 patients were ER and PgR-negative by both assays, suggesting hormonal independence as the mechanism for resistance in this group. In a subset of patients with receptor assays both prior to tamoxifen and at the time of progression while taking the drug, we found that most ER-positive tumors converted to an apparent ER-negative status when assayed by LBA, while PgR status frequently remained unchanged. The continued expression of ER and/or PgR in many patients with tumor progression on tamoxifen indicates that mechanisms for resistance other than receptor loss are common in breast cancer.Deceased     

乳腺癌干细胞相关亚群细胞周期分析

目的：流式细胞仪分选乳腺癌细胞系MCF-7的肿瘤干细胞相关SP亚群（side population，SP），并检测SP和非SP细胞周期。方法：MCF-7细胞悬液经Hoeehst33342染色，流式细胞仪分选SP和非SP后，乙醇固定，PI染色，流式细胞仪检测细胞周期。结果：SP细胞在MCF-7细胞中占4％，Vempamil阻断后比例减为0．5％。SP细胞中S／G2／M期细胞最低，仅占7．9％，而非SP细胞增殖期比例相对高，S／G2／M期细胞约占34．2％。未分选细胞中S／G2／M期细胞比例居中，为22．9％。结论：人乳腺癌细胞系MCF-7含SP亚群，比例约为4％，且SP细胞多处于静止期，具有一般干细胞的特性。     

乳腺癌干细胞相关亚群细胞周期分析

目的:流式细胞仪分选乳腺癌细胞系MCF-7的肿瘤干细胞相关SP亚群(side population,SP),并检测SP和非SP细胞周期。方法:MCF-7细胞悬液经Hoechst33342染色,流式细胞仪分选SP和非SP后,乙醇固定,PI染色,流式细胞仪检测细胞周期。结果:SP细胞在MCF-7细胞中占4%,Verapamil阻断后比例减为0·5%。SP细胞中S/G2/M期细胞最低,仅占7·9%,而非SP细胞增殖期比例相对高,S/G2/M期细胞约占34·2%。未分选细胞中S/G2/M期细胞比例居中,为22·9%。结论:人乳腺癌细胞系MCF-7含SP亚群,比例约为4%,且SP细胞多处于静止期,具有一般干细胞的特性。     

Estrogen sulfates: Biological and ultrastructural responses and metabolism in MCF-7 human breast cancer cells

The biological effects and ultrastructural alterations by different estrogen-3-sulfates (E₁-3-S and E₂-3-S) and estradiol-17-sulfate (E₂-17-S) were studied in the MCF-7 mammary cancer cell line in culture. The estrogen-3-sulfates very significantly stimulated the progesterone receptor (PR). The values (in pmoles/mg DNA ± SE) were: control, 0.46 ± 0.09; E₁-3-S, 2.24 ± 0.30, and E₂-3-S, 2.56 ± 0.45. The value of PR after E₂-17-S incubation (0.56 ± 0.24) was similar to the non-treated cells. The PR values obtained by the incubation of unconjugated estrone and estradiol were: 2.63 ± 0.45 and 2.27 ± 0.36, respectively. Analysis of the unconjugated estrogens in the medium indicated significant hydrolysis of estrogen-3-sulfates but not of E₂-17-S. Using [³H]-E₁-3-S, an important transformation was observed inside the cells, a great part being converted to estradiol (>60% in the nuclear fraction). Electron microscopic examination indicated alterations in the secretory system after incubation with estrogen-3-sulfates similar to those obtained with unconjugated estradiol. The effect provoked by E₂-17-S was significantly less than for the other sulfates.As estrogen sulfates are quantitatively the most important form of estrogens in the mammary gland, it is suggested that estrogen-3-sulfates play an important role in the biological responses to estrogens in breast cancer.     

Effects of tamoxifen and 4-hydroxytamoxifen on synchronized cultures of the human breast cancer cell line MCF-7

Summary The effect of antiestrogens on cultures of synchronized MCF-7 human breast cancer cells was studied. Cultures were synchronized by an eighteen hour block with 1.5mM hydroxyurea. Tamoxifen or 4-hydroxytamoxifen was added at various times following removal of the hydroxyurea block and the cell number and rate of incorporation of³H-thymidine by the cultures were followed for 48 hours through two waves of DNA synthesis. Antiestrogens added when hydroxyurea was removed inhibited only the second wave of DNA synthesis. Inhibition of the second wave only occurred if the antiestrogen was added before or at about the time of mitosis. To determine whether antiestrogen had to be present before mitosis in order to block the next round of DNA synthesis, cells in mitosis were selected by shaking them loose. The subsequent division of these cells was followed to determine the effect of treating them with antiestrogens before, after, or both before and after mitosis. The addition of antiestrogens at the time of mitosis proved sufficient to block the next round of cell division. Thus antiestrogens are cell cycle specific agents and appear to act at a point early in G₁ to block the next round of DNA synthesis and cell division.     

Cell cycle expression of estrogen receptors determined by image analysis on human breast cancer cellsin vitro andin vivo

Summary We have investigated, by image analysis, the cell cycle expression of estrogen receptors (ER) on MCF-7 cell line and on MCF-7 xenografts. The results demonstrate,in vitro as well asin vivo, an increase of ER concentration during the G0/G1-phase, followed by a decrease during the S-phase until the late S-phase where a rapid increase was noted. These results confirm that estrogens are involved in the DNA synthesis since ER is expressedin vivo at a maximal level in the late G1. In presence of saturating concentrations of 17 -estradiol, the mean ER concentration in G0/G1 phase is significantly decreased compared with the control cells cultured in estrogen-deprived medium. This indicates that 17-estradiol down-regulates ER preferentially in the G0/G1 phase. These data suggest that ER in S and G2/M phases is unable to interact with its ligand. Consequently, estrogens may have no effects on the entry of cells in mitosis. Finally, after long-term tamoxifen treatment of MCF-7 xenografts, a tamoxifen-resistant tumor was developed which was characterized by a change in the profile of ER concentration during the G0/G1 phase. In conclusion, it is possible that the differences in cell cycle distribution of ER could be correlated with different phenotypes of breast cancer and also with different clinical phases of tumoral evolution. However, it remains to be known what is the clinical significance of the ER cell cycle expression in relation to tumor aggressiveness and survival.     

Influence of the menstrual cycle on the concentrations of estrogen and progesterone receptors in primary breast cancer biopsies

Summary There is controversy in the literature regarding the effects of endogenous hormones on estrogen receptors (ER) and progesterone receptors (PR) in young women with breast cancer.We studied 117 young women with primary breast cancer and assessed their breast biopsies for ER and PR. The women had a record of their last menstrual period prior to breast biopsy. The menstrual cycle was divided into four phases — early proliferative (days 1–7), late proliferative (days 8–15), early secretory (days 16–22), and late secretory (days 23–30). There were lower levels of both ER and PR in biopsies excised during the early secretory phase than in other phases of the cycle; early proliferative phase receptor positive medians of ER = 77 fmol/mg protein and PR = 467 fmol/mg protein fell to ER = 28 fmol/mg and PR = 128 fmol/mg protein in the early secretory phase.     

Variability of steroid receptors in multiple biopsies of breast cancer: Effect of systemic therapy

Summary Estrogen receptor (ER) was measured on two or more specimens taken from each of 53 patients with carcinoma of the breast (18 also had progesterone receptor analyzed). Among the 35 patients who had no interval therapy, 27 patients had repeated tests within one month, and only two had reversal of ER results. Among the eight patients who had ER tests 9–36 months apart, four of five ER + lesions (7 + fmol/mg cytosol protein) had ER – metastasis. Among the 18 patients who received systemic therapy, three of ten ER + became ER –, while two of ten ER – became ER +. Our data and reports in the literature are summarized, showing that about 20% of receptor studies among multiple samples are different even when patients received no interval therapy. In asynchronous studies, it is more likely to have ER positive change to negative than vice versa (31% vs 12%). Interval chemotherapy or endocrine therapy tends to increase the occurrence of ER negative relapse among patients with ER positive tumors.     

稳定转染ERβ基因对MCF-7乳腺癌细胞系生长特性的影响

目的研究在不同处理因子作用下,外源基因ERβ的表达对MCF-7乳腺癌细胞系生长特性的影响。方法利用lipofectamine 2000将ERβ真核表达载体pCDNA3,ERβ导入MCF-7乳腺癌细胞系。采用含雌激素应答元件（ERE）的荧光素酶报告基因及Western blot方法,检测转染细胞中ERβ的转录活性和蛋白表达水平,筛选阳性克隆。以亲本细胞MCF-7及转染空载体质粒pCDNA3的MCF-7细胞为对照,在雌激素E2和雌激素受体拮抗剂4-OHT作用下观察细胞的生长特点。结果在转染ERβ基因的MCF3细胞系中,ERβ的转录激活活性明显升高;Western blot检测证实,ERβ的蛋白表达水平显著增高。在无处理因子情况下,外源基因ERβ在MCF-7细胞系中的表达对细胞的形态及生长速度无明显影响。与亲本细胞MCF-7及转染空载体质粒的MCF-7细胞相比,稳定转染ERβ的MCF-7细胞对雌激素的敏感性下降,但对4-OHT处理的敏感性无明显减少。结论外源性ERβ基因在MCF-7乳腺癌细胞中的稳定表达不增加对4-OHT的耐药性,但使之对雌激素的敏感性下降。     

Presurgical radiotherapy decreases the concentrations of estrogen and progesterone receptors in human breast cancer: A 200-patient study

Summary The concentrations of cytosol estrogen (RE) and progesterone (RP) receptors were evaluated in human breast cancer either pretreated or untreated by radiotherapy. Receptor sites were assayed within a week following surgery by using the classical dextran-coated charcoal technique with three saturating concentrations of (³H) 17 estradiol and (³H) R5020 and by correcting for nonsaturable binding estimated in parallel with an excess of nonradioactive ligand. Only tissue containing cancer cells as determined by a pathologist was assayed for receptors.Two nonrandomised groups were compared: a control group of 91 patients which were not treated before surgery, and an irradiated group of 108 patients which received radiotherapy (60 to 70 grays) about 2 to 4 months before surgery. Radiotherapy significantly reduced the percentage of receptor positive tumors ( 10 fmoles/mg protein) from RE 82% and RP 67% in the control group to RE 54% and RP 28% in the irradiated group.The mean concentrations of the positive receptors were also decreased by irradiation, from 238 fm/mgP and 146 fm/mgP to 55 fm/mgP and 54 fm/mgP for RE and RP respectively. This decrease was observed for all histopathological stages studied in both pre- and postmenopausal patients, and was also not dependent on cell density. Since the irradiated patients mostly had tumors of TNMT₂ and nonirradiated patients had smaller tumors (TNM T₂), we checked that the same effect of radiotherapy was found in the homogeneous group of TNM = T₂.We conclude that presurgical radiotherapy of breast cancer decreases the percentage of estrogen receptor and progestin receptor positive patients. Therefore, the assay of steroid receptors in breast cancer remains useful in predicting hormone dependency and prognosis of breast cancer when receptor concentrations are positive. But the assay is of no value when receptor concentrations are negative. New micro techniques must therefore be developed for assaying receptor before any therapy.     

Estrogen receptors,progesterone receptors,and cell proliferation in human breast cancer

Summary The breast is a target organ for estrogens and progesterone. These hormones control several functions of the normal and abnormal mammary epithelium including cell proliferation. Most of the actions of estrogens and progesterone are mediated via specific steroid receptors, and one would expect that proliferating cells should contain estrogen receptors (ER) and/or progesterone receptors (PR). However, the correlation between receptor expression and cell proliferation is still controversial. In the present study we have examined 29 human breast cancer samples; in 17 of them we evaluated the simultaneous ER and PR localization with that of proliferating cell nuclear antigen (PCNA) and silver-stained nucleolar organizer regions (AgNORs) in a cell-by-cell study. We found that in almost 50% of the tumor biopsies examined, the cells expressing ER were significantly associated with elevated cell proliferation. In another group (38%) there were not significant differences between ER expression and cell proliferation. In only one of the samples (6%) the cells expressing ER showed lower cell proliferation. The study also revealed that in 44% of the tumors the PR expressing cells were associated with elevated cell proliferation. In a second group the PR expression was not significantly associated with cell proliferation (33% of the cases). Finally, in 22% of the samples the cells carrying PR showed lower cell proliferation. We also detected lower ER immunoreactivity in 30% of the breast cancer biopsies with one of the monoclonal antibodies against ER (antibody 1D5 directed against the A/B domain). This group of tumors was PR-negative (or very weakly positive) and had high proliferation. The presence of tumors with abnormal ER proteins and displaying ER/PR significantly associated with elevated cell proliferation could have implications in human breast cancer treatment.     

补骨脂素逆转人乳腺癌细胞多药耐药性的研究

目的研究中药补骨脂素对人乳腺癌细胞多耐药性的逆转作用.方法用MTT法测定药物的细胞毒性和IC50用流式细胞仪测定耐药细胞P170糖蛋白表达,并选异搏定作阳性对照,观察具有钙拮抗作用的补骨脂素对MCF-7/ADR多药耐药性的逆转作用.结果补骨脂素在非细胞毒性剂量下能使MCF-7/ADR对阿霉素的浓度升高,但对细胞表面的糖蛋白P-170却没有影响.结论补骨脂素具有逆转人乳腺癌MCF-7/ADR多药耐药性的作用.     

Nitrosourea and nitrosocarbamate derivatives of the antiestrogen tamoxifen as potential estrogen receptor-mediated cytotoxic agents in human breast cancer cells

Summary We have prepared two analogs of the antiestrogen tamoxifen that incorporate known DNA-crosslinking functions, a chloroethyl nitrosourea and a nitrosocarbamate moiety, and we have tested their bioactivities in cultures of human breast cancer cells. Both compounds bind to the estrogen receptor from MCF-7 cells, with relative binding affinities of 0.18% for the nitrosocarbamate derivative and 0.35% for the nitrosourea derivative, while the affinity of tamoxifen is 1.8%, and that of estradiol is set at 100%. The tamoxifen-nitrosocarbamate compound demonstrated a dose-related cytotoxicity by the colony formation and cell proliferation assays that was not blocked by estradiol in either estrogen receptor-positive MCF-7 cells or estrogen receptor-negative MDA-MB-231 cells, and thus, was not studied further. Tamoxifen-nitrosourea (TAM-NU) showed dose-related cytotoxicity in MCF-7 cells that was blocked by estradiol, whereas its activity in MDA-MB-231 cells was unaffected by estradiol. N-2-(4-t-butylphenoxy)ethyl-N-chloroethyl-N-nitrosourea (BPE-NU), a control compound which contains the nitrosourea moiety but does not bind to the estrogen receptor, had no effect on cell proliferation or colony formation in MCF-7 cells, but was very inhibitory in the receptor-negative MDA-MB-231 cells. In contrast, TAM-NU was more active in the receptor-positive MCF-7 cells than in the MDA-MB-231 line. Thus, because TAM-NU appears to be active selectively against the receptor-positive cell line, and because this activity is suppressible by estradiol, its cytotoxic effect seems to be mediated via the estrogen receptor. However, since TAM-NU is active only in prolonged treatment protocols, it appears likely that its cytotoxic activity results from the hormone antagonistic effect of the hydrolysis product of TAM-NU (bis-desmethyltamoxifen), rather than from a direct receptor-mediated, DNA-directed cytotoxic action of TAM-NU itself. This study stresses the need for the use of appropriate control compounds and cell systems in order to assess whether the toxic activity displayed by hormone-cytotoxic conjugates is mediated by receptor interactions and whether it operates through the intended toxic mechanism.     

A model to describe how a point mutation of the estrogen receptor alters the structure-function relationship of antiestrogens

Summary The antiestrogen tamoxifen [(Z)-1(p--dimethylamino-ethoxyphenyl)-1,2-diphenylbut-1-ene] is an effective anticancer agent for the treatment of hormone responsive breast cancer. Previous studies have demonstrated that a point mutation in the estrogen receptor (ER) resulted in an alteration of the pharmacology of 4-hydroxytamoxifen, the active metabolite of tamoxifen (Jianget al, Mol Endocrinol 6:2167-2174, 1992). We have extended our studies to evaluate the effect of a point mutation, a Val substitution for Gly at amino acid 400 in the ligand binding domain of ER, on the pharmacology of other antiestrogens in ER stable transfectants derived from the ER-negative breast cancer cell line MDA-MB-231 CL10A. The compounds were tested with or without estradiol-17 (E₂) for their effects on cell growth in cells expressing the wild type ER (S30) or the mutant ER (ML2H) or in control antisense ER transfectant AS23 which does not express ER protein. MCF-7 cells, which express the wild type ER, were also used as a control. The growth of AS23 cells was not affected by any of the compounds at a concentration of 1 µM. E₂ stimulated the growth of MCF-7 cells but inhibited the growth of ER transfectants S30 and ML2H. The ML2H cells were about 10 to 100-fold less sensitive to E₂ and antiestrogens than S30 and MCF-7 cells. Keoxifene, an antiestrogen with a high affinity for the ER, maintained antiestrogenic activities in both ER transfectants and MCF-7 cells. However, the pharmacology of the steroidal antiestrogen RU 39411 was altered in the ML2H cells. The compound did not block the effects of E₂ but acted as an estrogen. Overall, this and previous studies from this laboratory demonstrate that it is possible to predict that the mutation will enhance the estrogenic activity of antiestrogens which have a side chain projecting in a position analogous to that of 4-hydroxytamoxifen. In contrast, compounds that do not have a side chain that occupies the same area, e.g. keoxifene and ICI 164,384, are unaffected by the mutation.We have extended our previous model (Liebermanet al, J Biol Chem 258:4741-4745, 1983) to incorporate our new observations.This article is dedicated to the memory of William L. McGuire, M.D., mentor and close friend for 20 years.     

乳腺癌内分泌治疗耐药相关机制的研究进展

内分泌治疗作为雌激素受体（estrogen receptor,ER）阳性乳腺癌的主要治疗方案被广泛应用。他莫西芬（tamoxifen,Tam）是乳腺癌内分泌治疗最常用的药物,它通过与雌激素竞争性结合ERα来降低雌激素的生物学活性,抑制细胞的增殖,从而治疗乳腺癌。然而,肿瘤细胞所表现出的原发性或获得性的他莫西芬耐药使得其临床应用受到了限制,寻找克服他莫西芬耐药的治疗策略已经刻不容缓。目前为止,他莫西芬耐药的相关机制已部分明确,但仍需进一步研究。有证据表明ERα、生长因子受体信号通路及microRNA的表达异常等多种机制均与他莫西芬耐药有关。本文对他莫西芬耐药的相关机制进行了具体分析,以期为ER阳性乳腺癌的治疗提供新思路。     

Changes in hormone receptors and proliferation markers in tamoxifen treated breast cancer patients and the relationship with response

Aim: To determine the effects of tamoxifen on the levels of hormone receptors and proliferation markers in the early phase of treatment and the relationship of the changes with tumor response in patients with primary breast cancer. Methods: Twenty-one women with primary, operable breast carcinomas were treated with tamoxifen 20 mg daily. Fine needle aspiration (FNA) was used to obtain samples prior to the start and at 14 days and 8-weeks post-treatment. From these samples estrogen receptor (ER), progesterone receptor (PgR), and Ki67 levels were determined using immunocytochemistry and ploidy and S-phase fraction (SPF) using flow cytometry. Tumor response was measured clinically according to UICC criteria. Results: There were 12 responders (2 CR, 10 PR) and 9 non-responders (2 NC, 7 PD). Responders were more likely to be ER + (p=0.002), PgR + (p=0.006), and low SPF (p=0.06). At 14 days post-tamoxifen, the median decrease in Ki67 (% cells staining) for responders was – 4.8 and for non-responders – 0.15 (p=0.005). This decrease was seen predominantly in ER + tumours. The difference in SPF was not significant. A decrease in ER was seen in 3/15 patients all of whom were responders. A rise in PgR was seen in 7/17 patients and all but one were responders. Similar changes for ER and PgR were seen at 8-weeks post-tamoxifen, although the reductions in Ki67 and SPF at that time point were not related to response. Conclusion: We have observed a decrease in Ki67 and ER and a rise in PgR after 14 days of treatment with tamoxifen that was related to subsequent response. This is the first study in which an early decrease in a proliferation marker has been shown to relate to subsequent clinical response.     

Mechanisms of hormone resistance in breast cancer

Summary At least half of all advanced breast cancers are positive for estrogen receptor (ER) and progesterone receptor (PR), but many nevertheless fail to respond to endocrine therapy. Studies of breast cancer cell lines and breast tumor specimens are beginning to reveal molecular heterogeneity of the receptors in subpopulations of these cells, leading to altered receptor function and sometimes to hormone resistance. Here we will review the data on molecular and cellular heterogeneity involving ER and PR, and possible underlying mechanisms of resistance to tamoxifen and progestins.     

Flow cytometry: Potential utility in monitoring drug effects in breast cancer

Summary Flow cytometric analysis of DNA ploidy and S-phase fraction are well recognized prognostic indicators in breast cancer. The present paper deals with the widening of the applications of flow cytometry to monitoring the effectiveness of antiestrogen therapy, detecting clonal selection and emergence of drug resistance, and monitoring chemosensitizing properties of drugs. Antiestrogen activity can be studied by DNA flow cytometry to address clinical research problems such as patient-specific pharmacokinetics, dosing compliance, and acquired antiestrogen resistance. Patient plasma specimens containing various concentrations of triphenylethylenes can be monitored for drug-induced effects using cell cycle measurements and correlated toin vivo drug levels. DNA flow cytometry has also been instrumental in the study of the effects of prolonged low-dose (0.5 µM for > 100 days) tamoxifen treatment on human estrogen receptor negative MDA-MB-231 cells, where it was shown that tamoxifen may significantly alter cell cycle kinetics and tumorigenicity of these cells, selecting a new, more aggressive, and rapidly growing clone. Lastly, it has been shown that the chemosensitizing properties of another triphenylethylene antiestrogen, toremifene, on estrogen receptor negative, multidrug resistant MDA-MB-231-A1 human breast cancer cells can be studied using flow cytometric analysis. Toremifene (and its metabolites N-desmethyltoremifene and toremifene IV) are able to resensitize MDA-MB-231-A1 cells to vinblastine and doxorubicin, as reflected in a marked shift of cells to G₂/M phase of the cell cycle. Flow cytometry is a widely available technique that might be applied clinically to monitor, at the cellular level, drug effects on tumors, including the modulators of drug resistance.